1. Field of the Invention
The present invention generally relates to a system for reproducing dynamics behavior of an automobile or motor vehicle, i.e., vehicle dynamics behavior reproduction system which is designed for improving the accuracy of analysis of the dynamics behavior of the motor vehicle by taking into consideration the driving situation to thereby improve the accuracy of analysis of a premonitory sign of e.g. traffic accident. More particularly, the present invention is concerned with the vehicle dynamics behavior reproduction system which is capable of describing the dynamics behavior of the motor vehicle with high accuracy up to a critical or marginal stability (limit of stability) by adapting the cornering stiffnesses at individual wheels of the motor vehicle to the driving situations.
2. Description of Related Art
In recent years, there has been an increasing trend of using a vehicle model with a view to improving the system for controlling the motion of the motor vehicle.
The vehicle model is a system to describe the behavior of the motor vehicle from a standpoint of the motor vehicle dynamics (i.e., the vehicle dynamics behavior in short). In this connection, it is noted that technologies of high level have been proposed for setting up a nonlinear state space model and a nonlinear state observer among others. For more particulars of these technologies, reference may have to be made to e.g. U. Kiencke and L. Nielsen: “AUTOMOTIVE CONTROL SYSTEMS”, Springer-Verlag, Berlin, Heidelberg, New York, 2000. Hereinafter, this publication will be referred to as the literature [1].
In the conventional system based on the vehicle behavior dynamics, the vehicle behavior is described primarily with a linear one track vehicle model while neglecting rolling and pitching of the vehicle. In this conjunction, reference may have to be made to M. Mitschke: “DYNAMIK DER KRAFTFAHRZEUGE”, Volume C of “FAHRVERHALTEN”, Springer-Verlag, Berlin, Heidelberg, New York, 2nd Edition, 1990. Hereinafter, this publication will be referred to as the literature [2].
Further, as the simplified system known heretofore, there has also been proposed such a system in which a proportionality factor termed “cornering stiffness” is presumed in association with the relation between a side slip angle of tire (hereinafter also referred to as the tire side slip angle only for the convenience of description) and a side or lateral force acting on a wheel (hereinafter also referred to as the lateral wheel force). For more particulars, reference may have to be made to e.g. DE 198 12 237 C1 and DE 198 51 978 A1.
The vehicle dynamics behavior reproduction system for the simplified vehicle motion control system known heretofore suffers a problem that in the situation where the lateral acceleration of the motor vehicle is relatively high, behavior of the tire becomes nonlinear and thus the presumption of the linear (proportional) relation between the tire side slip angle and the lateral wheel force can no more be relied, incurring thus significant degradation in the reliability of the result of vehicle behavior reproduction, as a result of which description of the vehicle motion with the aid of the vehicle model is rendered invalid in the situation where the acceleration of the motor vehicle in the lateral direction is high (e.g. not lower than 4 m/s2).